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Volume 32, Number 8—August 2026
Research
Rapid Expansion of Highly Pathogenic Avian Influenza A(H5N1) Clade 2.3.4.4b Genotype D1.1 Virus across Flyway Regions, North America, Fall 2024
Matthew Scotch
, Temitope O.C. Faleye, Angelica Urquidez-Negrete, Arvind Varsani, Ann Fan, and Anne Justice-Allen
, Temitope O.C. Faleye, Angelica Urquidez-Negrete, Arvind Varsani, Ann Fan, and Anne Justice-Allen
Table 1
Timing of expansion of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b genotype D1.1 virus across flyway regions, North America, fall 2024*
| Dataset | tMRCA, y (95% HPD) | Date (range) | Evolution rate × 10−3 substitutions/site/year (95% HPD) |
|---|---|---|---|
| Hemagglutinin | 0.80 (0.69–0.94) | 2024 Jun 27 (2024 May 8–Aug 5) | 7.16 (6.59–7.75) |
| Concatenated | 0.74 (0.69–0.81) | 2024 Jul 19 (2024 Jun 25–Aug 6) | 5.56 (5.06–6.04) |
*Timing calculated from hemagglutinin and concatenated datasets. Both datasets had the same 660 taxa from October 2024–April 2025. HPD, highest posterior density; tMRCA, time to most recent common ancestor.
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Page updated: July 13, 2026
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